SARS-CoV-2 Seroprevalence in Employees of Four Essential Non–Health Care Sectors at Moderate/High Risk of Exposure to Coronavirus Infection

Objective to evaluate SARS-CoV-2 seroprevalence in Swiss non-healthcare employees at a moderate to high risk of exposure: bus drivers; supermarket, laundry service, and mail-sorting center employees. Methods Data on 455 essential workers included demographics, SARS-CoV-2 exposure and use of protective measures. Anti-SARS-CoV-2 IgG and IgA targeting the spike protein were measured between May and July 2020. Results The overall crude seroprevalence estimate (15.9%, 95% CI = 12.6-19.7) among essential workers was not significantly higher than that of the general working-age population (11.2%, 95% CI = 7.1-15.2). Seroprevalence ranged from 11.9% (95% CI = 6.3-19.8) among bus drivers to 22.0% (95% CI = 12.6-19.7) among food supermarket employees. Conclusions We found no significant difference in seroprevalence between our sample of essential workers and local working-age population during the first lockdown phase of the COVID-19 pandemic. Having a seropositive housemate was the strongest predictor of SARS-CoV-2 seropositivity.